JP2014211166A - Device for controlling drive train of work vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow reduction in a size of an engine 70 while securing an output torque in a low rotation range of the engine 70 without using a supercharger in a work vehicle 141.SOLUTION: A work vehicle 141 includes: an engine 70 mounted to a travelling machine body 142; and a common rail-type fuel injection device 117 for injecting fuel into the engine 70. The work vehicle is configured to be able to change a minimum rotation speed Na of the engine 70 in a range where the minimum rotation speed Na is faster than a low-idle rotation speed Nlow specific to the engine 70.

Description

  The present invention relates to a drive system (engine or continuously variable transmission) control device for a work vehicle such as an agricultural machine or a construction machine.

  In order to downsize the engine while maintaining the rated output, the engine displacement is generally reduced and a supercharger is incorporated (see, for example, Patent Document 1). Such downsizing makes it possible to reduce the size and weight of a work vehicle equipped with an engine and improve fuel efficiency.

Special table 2008-514854

  However, reducing the displacement and using the turbocharger for downsizing increases the number of parts and increases the cost, and the output torque in the low rotation range is smaller than that of the engine before reducing the displacement. There was a problem that it was difficult to secure.

  In view of this, the present invention has a technical problem to provide a drive system control device for a work vehicle that solves such problems.

  According to a first aspect of the present invention, there is provided a work vehicle drive system control device including: an engine mounted on a traveling machine body; and a common rail fuel injection device that injects fuel into the engine. The minimum rotation speed can be changed within a range in which the minimum rotation speed is higher than the inherent low idle rotation speed.

  According to a second aspect of the present invention, the work vehicle drive system control device according to the first aspect further includes a continuously variable transmission that shifts power from the engine, and the minimum rotational speed is set to be lower than the low idle rotational speed. Is set to a larger value, the speed ratio of the continuously variable transmission is changed and adjusted so that the minimum vehicle speed of the traveling machine remains unchanged at the low idle rotation speed.

  According to a third aspect of the present invention, there is provided a drive system control device for a work vehicle according to the second aspect, wherein the engine operating point relating to the rotational speed and torque of the engine deviates from a preset optimum fuel consumption line. The driving point is shifted to the optimum fuel consumption line, and the speed ratio of the continuously variable transmission is changed and adjusted so as not to change the vehicle speed of the traveling machine body.

  According to the drive system control device for a work vehicle according to the first aspect of the present invention, in the work vehicle including the engine mounted on the traveling machine body and the common rail fuel injection device that injects fuel into the engine, the engine Since the minimum rotational speed of the engine can be changed within a range that is larger than the low idle rotational speed inherent to the engine, a high output horsepower can be easily ensured as compared with the engine having the same displacement. In other words, the engine can have a lower displacement than that of the engine with the same output horsepower. Therefore, the engine downsizing can be easily realized. In addition, since a supercharger is not required to secure output horsepower, there is an effect that the cost of parts can be suppressed.

  According to a second aspect of the present invention, the continuously variable transmission for shifting the power from the engine is provided, and when the minimum rotational speed is set to a value larger than the low idle rotational speed, Since the speed ratio of the continuously variable transmission is changed and adjusted so that the vehicle speed remains unchanged at the low idle rotational speed, even if the minimum rotational speed is higher than the low idle rotational speed, Thus, the minimum vehicle speed is not increased and can be maintained at the low idle rotation speed. For this reason, at the time of low speed driving | running | working, there exists an effect that the driving | running performance (vehicle speed without a sense of incongruity) which is the same as the work vehicle carrying the same displacement as the said engine is obtained.

  According to a third aspect of the present invention, in the drive system control device for a work vehicle according to the second aspect, when the engine operating point related to the rotational speed and torque of the engine deviates from a preset optimum fuel consumption line, While shifting the engine operating point on the optimum fuel consumption line and changing and adjusting the gear ratio of the continuously variable transmission so as not to change the vehicle speed of the traveling machine body, while performing fuel-efficient driving, It is possible to reliably prevent the vehicle speed fluctuation accompanying the change in the rotational speed. Therefore, in the work vehicle, there is an effect that stable traveling performance can be obtained.

It is a side view of the tractor as a work vehicle. It is a top view of a tractor. It is a hydraulic circuit diagram of a tractor. It is a skeleton figure of the power transmission system in a tractor. It is a figure explaining the relationship between a vehicle speed and the gear ratio of a continuously variable transmission. It is fuel system explanatory drawing of an engine. It is a functional block diagram which shows the relationship between an engine and an exhaust gas purification apparatus. It is a functional block diagram which shows the relationship between ECU and a speed change controller. It is a figure explaining the injection timing of fuel. It is explanatory drawing of the output characteristic map in 1st Example. It is a flowchart which shows the flow of rotational speed limitation control. It is explanatory drawing of the output characteristic map in 2nd Example. It is a flowchart which shows the flow of minimum vehicle speed control. It is a flowchart which shows the detail of the gear ratio control in minimum vehicle speed control. It is a flowchart which shows the flow of optimal fuel consumption control. It is a flowchart which shows the detail of the gear ratio control during optimal fuel consumption control. It is explanatory drawing of the output characteristic map corresponding to another example of fuel-injection control. It is a flowchart which shows another example of fuel-injection control.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(1). Schematic Structure of Tractor First, the schematic structure of a tractor 141 that is an example of a work vehicle will be described with reference to FIGS. 1 and 2. As shown in FIGS. 1 and 2, the traveling machine body 142 of the tractor 141 is supported by a pair of left and right front wheels 143 and a pair of left and right rear wheels 144. The tractor 141 is configured to travel forward and backward by driving the rear wheel 144 and the front wheel 143 with the engine 70 mounted on the front portion of the traveling machine body 142. The engine 70 is covered with a hood 146. A cabin 147 is installed on the upper surface of the traveling machine body 142. Inside the cabin 147, a steering seat 148 and a steering handle 149 for moving the steering direction of the front wheel 143 to the left and right by steering are installed. A step 150 where the operator gets on and off is provided on the outer side of the cabin 147, and a fuel tank 151 for supplying fuel to the engine 70 is provided on the inner side of the step 150 and below the bottom of the cabin 147. .

  As shown in FIGS. 1 and 2, the steering handle 149 in the cabin 147 is provided on a steering column 190 located in front of the steering seat 148. A throttle lever 197 for setting and maintaining the rotational speed of the engine 70 and a pair of left and right brake pedals 191 for braking the traveling machine body 142 are provided on the right side of the steering column 190. On the left side of the control column 190, a forward / reverse switching lever 198 and a clutch pedal 192 for switching the traveling direction of the traveling machine body 142 between forward and reverse are disposed. A parking brake lever 200 that holds the brake pedal 191 in the depressed position is provided on the back side of the steering column 190.

  An accelerator pedal 199 is disposed on the right side of the brake pedal 191. The accelerator pedal 199 increases / decreases the rotational speed in a range beyond this, with the rotational speed of the engine 70 set by the throttle lever 197 as the lower limit rotational speed. On the right column of the control seat 148, a work machine lifting lever 193 for manually changing and adjusting the height position of the rotary tiller 164 as a ground work machine, a PTO speed change lever 194, a main speed change lever 201 for speed change operation, etc. Is arranged. A sub-transmission lever 195 is disposed on the left column of the control seat 148, and a differential lock pedal 196 is disposed in front of the left column.

  As shown in FIGS. 1 and 2, the traveling aircraft body 142 includes an engine frame 154 having a front bumper 152 and a front axle case 153, and left and right aircraft frames 156 that are detachably fixed to the rear portion of the engine frame 154 with bolts. Consists of. A transmission case 157 is connected to the rear part of the body frame 156 for appropriately shifting the driving force of the engine 70 and transmitting it to the rear wheels 144 and the front wheels 143. The rear wheel 144 is attached via a rear axle case 158 mounted so as to protrude outward from the outer surface of the mission case 157. In the mission case 157, a continuously variable transmission 159 (see FIGS. 3 and 4) for shifting the driving force from the engine 70 is provided.

  On the rear upper surface of the mission case 157, a hydraulic working machine lifting mechanism 160 that lifts and lowers the rotary tiller 164 is detachably attached. The rotary cultivator 164 is connected to the rear portion of the mission case 157 via a three-point link mechanism including a pair of left and right lower links 161 and a top link 162. On the rear side surface of the mission case 157, a PTO shaft 163 for transmitting a PTO driving force to the rotary tiller 164 protrudes backward.

  As shown in FIGS. 1 and 2, a seeder 170 for sowing is attached to the rear side of the rotary tiller 164 so as to be exchangeable with a fertilizer spreader (not shown). The seeder 170 includes a tank 171 for putting seeds therein, a feeding unit 172 that feeds seeds in the tank 171 by a fixed amount, and an electric motor 173 that drives a feeding roller (not shown) of the feeding unit 172. The seeds in the tank 171 are sowed on the already cultivated ground behind the rotary tiller 164 from the feeding portion 172. In addition, when a fertilizer spreader is attached to the rotary tiller 164, the fertilizer (chemical | medical agent) of a fertilizer spreader will be spread on the already cultivated ground behind the rotary tiller 164.

(2). Next, the structure of the hydraulic circuit 210 of the tractor 141 will be described with reference mainly to FIG. The hydraulic circuit 210 of the tractor 141 includes a working hydraulic pump 204 and a traveling hydraulic pump 205 that are driven by the rotational power of the engine 70. The working hydraulic pump 204 and the traveling hydraulic pump 205 are provided on the front side of the front side wall member 222 in the mission case 157 (see FIG. 4). The working hydraulic pump 204 is connected to a control electromagnetic valve 211 for supplying hydraulic oil to the lifting control hydraulic cylinder 215 of the working machine lifting mechanism 160. The control solenoid valve 211 is configured to be switchable by operating the work implement lifting lever 193. When the control electromagnetic valve 211 is switched by the work implement lifting lever 193, the lift control hydraulic cylinder 215 is extended and contracted to lift the lift arm 169 that connects the work implement lifting mechanism 160 and the left and right lower links 161 (see FIG. 1). Rotate up and down. As a result, the rotary tiller 164 moves up and down via the lower link 161.

  The traveling hydraulic pump 205 supplies hydraulic oil to the continuously variable transmission 159 of the mission case 157 and the hydraulic cylinder 203 for power steering. In this case, the mission case 17 is also used as a hydraulic oil tank, and the hydraulic oil inside the mission case 157 is supplied to the hydraulic pumps 204 and 205. The traveling hydraulic pump 205 is connected to a power steering hydraulic cylinder 203 via a power steering control valve 212, while an automatic brake electromagnetic valve 246 for a brake cylinder 247 for a pair of left and right brake operating mechanisms 245 is provided. Is also connected.

  Further, the traveling hydraulic pump 205 is operated by a PTO clutch hydraulic electromagnetic valve 249 that operates the PTO clutch 248 of the PTO transmission mechanism 228, a proportional control valve 213 and a starting electromagnetic valve 217 for the continuously variable transmission 159, and the like. A switching valve 214, a high-speed clutch electromagnetic valve 251 for operating the auxiliary transmission hydraulic cylinder 250 of the auxiliary transmission mechanism 227, a forward clutch electromagnetic valve 253 for the forward hydraulic clutch 252 of the forward / reverse switching mechanism 226, and a reverse hydraulic clutch 254 Are connected to a four-stroke hydraulic solenoid valve 257 for the four-wheel drive hydraulic clutch 256 of the two-wheel drive and four-wheel drive switching mechanism 229, and a double speed hydraulic solenoid valve 259 for the double speed hydraulic clutch 258.

  The PTO clutch hydraulic solenoid valve 249, the forward clutch solenoid valve 253, the reverse clutch solenoid valve 255, the four-wheel drive hydraulic solenoid valve 257, and the double speed hydraulic solenoid valve 259 operate these clutch cylinders by appropriately controlling them. Thus, the hydraulic clutches 248, 252, 254, 256, and 258 are configured to be switched and driven. The hydraulic circuit 210 also includes a relief valve, a flow rate adjustment valve, a check valve, an oil cooler, an oil filter, and the like.

(3). Next, the power transmission system of the tractor 141 will be described with reference mainly to FIG. A front side wall member 222 is fixed to the front surface of the mission case 157 formed in a hollow box shape, and a rear side wall member 223 is detachably fixed to the rear surface. The interior of the mission case 157 is divided into a front chamber 224 and a rear chamber 225 by a partition wall 221. Although illustration is omitted, the front chamber 224 and the rear chamber 225 communicate with each other so that the internal hydraulic fluid can move between them. On the front chamber 224 side of the mission case 157, a forward / reverse switching mechanism 226 that switches the rotational power from the continuously variable transmission 159 in the forward or reverse direction and a mechanical type that shifts the rotational power via the forward / backward switching mechanism 226. The sub-transmission mechanism 227, the PTO transmission mechanism 228 for appropriately changing the rotational power from the engine 70 and transmitting it to the PTO shaft 163, and the two-wheel drive and four-wheel drive switching mechanism for switching between the two-wheel drive and the four-wheel drive of the front and rear wheels 143 and 144 229 is arranged. On the rear chamber 225 side, a continuously variable transmission 159 and a differential gear mechanism 230 that transmits rotational power via the auxiliary transmission mechanism 227 to the left and right rear wheels 144 are disposed.

  A flywheel 231 is attached to an engine output shaft 74 protruding rearward from the engine 70 so as to be directly connected. The flywheel 231 and the main shaft 232 extending rearward therefrom are connected via a main clutch 233 for power transmission. The main drive shaft 232 and the main transmission input shaft 234 projecting forward from the transmission case 157 are connected via a power transmission shaft 235 having universal shaft joints at both ends. The rotational power of the engine 70 is transmitted from the engine output shaft 74 to the main transmission input shaft 234 via the main driving shaft 232 and the power transmission shaft 235, and then appropriately shifted by the continuously variable transmission 159 and the auxiliary transmission mechanism 227. The transmission power is transmitted to the left and right rear wheels 144 via the differential gear mechanism 230. Shift power by the continuously variable transmission 159 and the auxiliary transmission mechanism 227 is also transmitted to the left and right front wheels 153 via the two-wheel drive / four-wheel drive switching mechanism 229 and the differential gear mechanism 236 in the front axle case 153.

  The continuously variable transmission 159 inside the rear chamber 225 is an inline type in which a main transmission output shaft 237 is concentrically arranged on a main transmission input shaft 234, and includes a variable displacement hydraulic pump unit 240 and the hydraulic pressure. And a constant displacement type hydraulic motor unit 241 that operates with high-pressure hydraulic fluid discharged from the pump unit 240. The hydraulic pump unit 240 is provided with a pump swash plate 242 that can change the inclination angle with respect to the axis of the main transmission input shaft 234 and adjust the amount of hydraulic oil supplied thereto. Associated with the pump swash plate 242 is a main transmission hydraulic cylinder 243 that changes and adjusts the inclination angle of the pump swash plate 242 with respect to the axis of the main transmission input shaft 234. By changing the inclination angle of the pump swash plate 242 by driving the main transmission hydraulic cylinder 243, the amount of hydraulic oil supplied from the hydraulic pump unit 240 to the hydraulic motor unit 241 is changed and adjusted, and the main transmission of the continuously variable transmission 159 is changed. A speed change operation is performed.

  That is, when the switching valve 214 is operated by hydraulic oil from the proportional control valve 213 that operates in proportion to the operation amount of the main transmission lever 201, the main transmission hydraulic cylinder 190 is driven, and accordingly, the main transmission input shaft 234 is driven. The inclination angle of the pump swash plate 242 with respect to the axis is changed. The pump swash plate 242 of the embodiment adjusts the angle in a range between one (positive) maximum inclination angle and the other (negative) maximum inclination angle with a neutral angle of substantially zero inclination (before and after including zero) interposed therebetween. It is possible to set the angle so that the vehicle body 142 is inclined at one of the lowest vehicle speeds (in this case, it is negative and the inclination angle near the maximum) (see FIG. 5).

  When the inclination angle of the pump swash plate 242 is substantially zero (neutral angle), the hydraulic motor unit 241 is not driven by the hydraulic pump unit 240 and the main transmission output shaft 237 is driven at substantially the same rotational speed as the main transmission input shaft 234. Rotates. When the pump swash plate 242 is tilted in one direction (positive tilt angle) with respect to the axis line of the main transmission input shaft 234, the hydraulic pump unit 240 increases the speed of the hydraulic motor unit 241 to operate the main transmission input shaft. The main transmission output shaft 237 rotates at a rotational speed faster than H.234. As a result, the rotational speed of the hydraulic motor unit 241 is added to the rotational speed of the main transmission input shaft 234 and transmitted to the main transmission output shaft 237. For this reason, in the range of the rotational speed higher than the rotational speed of the main transmission input shaft 234, the transmission power (vehicle speed) from the main transmission output shaft 237 is proportional to the inclination angle (positive inclination angle) of the pump swash plate 242. Be changed. When the pump swash plate 242 is positive and has an inclination angle near the maximum, the traveling machine body 142 reaches the maximum vehicle speed (see the white squares in FIG. 5).

  When the pump swash plate 242 is inclined in the other direction (negative inclination angle) with respect to the axis line of the main transmission input shaft 234, the hydraulic pump unit 240 operates the hydraulic motor unit 241 to decelerate (reverse) and shift the main transmission. The main transmission output shaft 237 rotates at a lower rotational speed than the input shaft 234. As a result, the rotational speed of the hydraulic motor unit 241 is subtracted from the rotational speed of the main transmission input shaft 234 and transmitted to the main transmission output shaft 237. Therefore, the transmission power from the main transmission output shaft 237 is changed in proportion to the inclination angle (negative inclination angle) of the pump swash plate 242 within the range of the rotation speed lower than the rotation speed of the main transmission input shaft 234. . When the pump swash plate 242 is negative and has an inclination angle near the maximum, the traveling machine body 142 has the minimum vehicle speed (see the white circles in FIG. 5).

  In the embodiment, when the switching valve 214 is operated with hydraulic fluid from a starting electromagnetic valve 217 that is operated in accordance with a command from a work machine (transmission) controller 271 described later, regardless of the operation position of the main transmission lever 201. The main transmission hydraulic cylinder 243 is driven, and accordingly, the inclination angle of the pump swash plate 242 with respect to the axis of the main transmission input shaft 234 is changed.

(4). Next, the structure of the engine 70 and its surroundings will be described with reference to FIGS. 6 and 7. As shown in FIG. 6, the engine 70 is a four-cylinder diesel engine, and includes a cylinder block 75 with a cylinder head 72 fastened on the upper surface. An intake manifold 73 is connected to one side of the cylinder head 72, and an exhaust manifold 71 is connected to the other side. A common rail device 117 that supplies fuel to each cylinder of the engine 70 is provided below the intake manifold 73 on the side surface of the cylinder block 75. An intake pipe 76 connected to the intake upstream side of the intake manifold 73 is connected to an intake throttle device 81 and an air cleaner (not shown) for adjusting the intake pressure (intake amount) of the engine 70.

  As shown in FIG. 7, the fuel tank 118 is connected to the injectors 115 for the four cylinders in the engine 70 via the common rail device 117 and the fuel supply pump 116. Each injector 115 is provided with an electromagnetic switching control type fuel injection valve 119. The common rail device 117 includes a cylindrical common rail 120. A fuel tank 118 is connected to the suction side of the fuel supply pump 116 via a fuel filter 121 and a low pressure pipe 122. The fuel in the fuel tank 118 is sucked into the fuel supply pump 116 via the fuel filter 121 and the low pressure pipe 122. The fuel supply pump 116 of the embodiment is disposed in the vicinity of the intake manifold 73. On the other hand, a common rail 120 is connected to the discharge side of the fuel supply pump 116 via a high-pressure pipe 123. The common rail 120 is connected to injectors 115 for four cylinders via four fuel injection pipes 126.

  In the above configuration, the fuel in the fuel tank 118 is pumped to the common rail 120 by the fuel supply pump 116, and high-pressure fuel is stored in the common rail 120. Each fuel injection valve 119 is controlled to open and close, whereby high-pressure fuel in the common rail 120 is injected from each injector 115 to each cylinder of the engine 70. That is, by electronically controlling each fuel injection valve 119, the injection pressure, injection timing, and injection period (injection amount) of the fuel supplied from each injector 115 are controlled with high accuracy. Therefore, nitrogen oxide (NOx) from the engine 70 can be reduced, and noise and vibration of the engine 70 can be reduced.

  As shown in FIG. 9, the common rail device 117 is configured to execute the main injection A in the vicinity of the top dead center (TDC). In addition to the main injection A, the common rail device 117 executes a small amount of pilot injection B for the purpose of reducing NOx and noise at a crank angle θ1 of about 60 ° before the top dead center, Pre-injection C is executed for the purpose of noise reduction immediately before the crank angle θ2, and particulate matter (hereinafter referred to as PM) is reduced and exhaust gas is emitted at the crank angles θ3 and θ4 after top dead center. The after-injection D and the post-injection E are executed for the purpose of promoting purification.

  The pilot injection B is injected at a timing that is greatly advanced with respect to the main injection A, thereby promoting the mixing of fuel and air. The pre-injection C is performed prior to the main injection A to shorten the ignition timing delay in the main injection A. After-injection D is injected at a time close to main injection A, thereby activating diffusion combustion and re-burning PM (reducing PM). The post-injection E is supplied to the DPF 50, which will be described later, as unburned fuel without contributing to the actual combustion process by being injected at a timing that is largely retarded with respect to the main injection A. The unburned fuel supplied to the DPF 50 reacts on a diesel oxidation catalyst 53 described later, and the exhaust gas temperature in the DPF 50 rises due to the reaction heat. The level of the peaks in the graph in FIG. 9 roughly represents the difference in the fuel injection amount at each of the injection stages A to E.

  As shown in FIG. 7, a fuel supply pump 116 is connected to the fuel tank 118 via a fuel return pipe 129. A common rail return pipe 131 is connected to the end of the cylindrical common rail 120 in the longitudinal direction via a return pipe connector 130 that limits the pressure of fuel in the common rail 120. That is, surplus fuel from the fuel supply pump 116 and surplus fuel from the common rail 120 are collected in the fuel tank 118 via the fuel return pipe 129 and the common rail return pipe 131.

  An exhaust pipe 77 connected to the exhaust downstream side of the exhaust manifold 71 includes an exhaust throttle device 82 for adjusting the exhaust pressure of the engine 70 and a DPF 50 (diesel particulate filter) as an example of an exhaust gas purification device. Connected. Exhaust gas discharged from each cylinder to the exhaust manifold 71 is purified through the exhaust pipe 77, the exhaust throttle device 82, and the DPF 50, and then released to the outside.

  As shown in FIG. 6, the DPF 50 is for collecting PM and the like in the exhaust gas. The DPF 50 according to the embodiment is configured by accommodating a diesel oxidation catalyst 53 such as platinum and a soot filter 54 in series in a substantially cylindrical filter case 52 in a casing 51 made of a heat-resistant metal material. A diesel oxidation catalyst 53 is disposed upstream of the filter case 52 and a soot filter 54 is disposed downstream of the exhaust. The soot filter 54 has a honeycomb structure having a large number of cells partitioned by porous partition walls that can filter exhaust gas.

  An exhaust introduction port 55 that communicates with the exhaust downstream side of the exhaust throttle device 82 in the exhaust pipe 77 is provided on one side of the casing 51. One side of the casing 51 and one side of the filter case 52 are closed by a first side wall plate 56 and a second side wall plate 57. The other side of the casing 51 is closed by a first lid plate 59 and a second lid plate 60. Between the two cover plates 59 and 60, an exhaust sound attenuation chamber 63 communicating with the filter case 52 via a plurality of communication pipes 62 is formed. Further, a substantially cylindrical exhaust outlet pipe 61 passes through the second lid plate 60. A plurality of communication holes 58 that open toward the exhaust sound attenuation chamber 63 are formed on the outer peripheral surface of the exhaust outlet pipe 61. The exhaust outlet pipe 61, the exhaust sound attenuation chamber 63, and the like constitute a silencer 64.

  An exhaust gas introduction pipe 65 is inserted into an exhaust introduction port 55 formed on one side of the casing 51. The tip of the exhaust gas introduction pipe 65 projects across the casing 51 to the side surface opposite to the exhaust introduction port 55. A plurality of communication holes 66 opening toward the filter case 52 are formed on the outer peripheral surface of the exhaust gas introduction pipe 65. A portion of the exhaust gas introduction pipe 65 that protrudes from the side surface opposite to the exhaust introduction port 55 is closed by a lid 67 that is detachably screwed to the portion.

  The DPF 50 is provided with a DPF differential pressure sensor 68 that detects a clogged state of the soot filter 54 as an example of a detection unit. The DPF differential pressure sensor 68 detects a pressure difference between the exhaust pressures upstream and downstream of the soot filter 54 in the DPF 50 (exhaust gas differential pressure between the inlet side and the outlet side). In this case, the upstream exhaust pressure sensor 68 a constituting the DPF differential pressure sensor 68 is attached to the lid 67 of the exhaust gas introduction pipe 65, and the downstream exhaust pressure is interposed between the soot filter 54 and the exhaust sound attenuation chamber 63. A sensor 68b is attached.

  Since there is a specific relationship between the pressure difference between the upstream and downstream of the DPF 50 and the PM accumulation amount in the soot filter 54 (DPF 50), based on the pressure difference detected by the DPF differential pressure sensor 68, The PM accumulation amount in the DPF 50 is obtained by calculation. Then, the regeneration control of the soot filter 54 (DPF 50) is executed by controlling the operation of the intake throttle device 81, the exhaust throttle device 82, or the common rail 120 based on the calculation result of the PM accumulation amount.

  In the above configuration, the exhaust gas from the engine 70 enters the exhaust gas introduction pipe 65 through the exhaust introduction port 55, and is ejected into the filter case 52 from each communication hole 66 formed in the exhaust gas introduction pipe 65. Then, the diesel oxidation catalyst 53 and the soot filter 54 are passed through in this order for purification treatment. PM in the exhaust gas is collected by the soot filter 54 (porous partition between each cell). Exhaust gas that has passed through the diesel oxidation catalyst 53 and the soot filter 54 is discharged from the exhaust outlet pipe 61 to the outside through the silencer 64.

When the exhaust gas passes through the diesel oxidation catalyst 53 and the soot filter 54, if the exhaust gas temperature exceeds a reproducible temperature (for example, about 250 to 300 ° C.), the action of the diesel oxidation catalyst 53 causes NO in the exhaust gas. (Nitric oxide) is oxidized to unstable NO ₂ (nitrogen dioxide). The PM collecting ability of the soot filter 54 is restored by oxidizing and removing the PM deposited on the soot filter 54 with O (oxygen) released when NO ₂ returns to NO. That is, the soot filter 54 (DPF 50) is regenerated.

(5). Configuration Related to Engine Control Next, a configuration related to control of the engine 70 will be described with reference to FIGS. As shown in FIGS. 7 and 8, the tractor 141 includes, as control means, an ECU 11 that operates a fuel injection valve 119 for each cylinder in the engine 70, and a work machine (transmission) controller 271. The ECU 11 includes a CPU 31 that executes various arithmetic processes and controls, a ROM 32 that stores various data in a fixed manner, an EEPROM 33 that stores control programs and various data in a rewritable manner, and a RAM 34 that temporarily stores control programs and various data. A timer 35 for measuring time, an input / output interface, and the like. The work machine controller 271 also has a CPU 281, a ROM 282, an EEPROM 283, a RAM 284, a timer 285, an input / output interface, and the like, like the ECU 11.

  As a guideline, the ECU 11 and the work machine controller 271 that are the control means are combined and controlled so that the length of the harness of the input / output system equipment is as short as possible. (Omitted). The ECU 11 and the work machine controller 271 are electrically connected to each other via a CAN communication bus 272. ECU11 of embodiment is arrange | positioned at the engine 70 or its vicinity (refer FIG. 2). The work machine controller 271 is disposed, for example, below the control seat 148 in the cabin 147 (see FIG. 2). Note that three or more control means may be connected via a communication bus. Each input / output system device to be described later may be connected to any control means.

  On the input side of the ECU 11, at least a rail pressure sensor 12 that detects the fuel pressure in the common rail 120, an electromagnetic clutch 13 that rotates or stops the fuel pump 116, and the rotational speed of the engine 70 (camshaft position of the engine output shaft 74). Engine speed sensor 14 as a rotational speed detection means to detect, injection setter 15 for detecting and setting the number of fuel injections of the injector 115 (number of times during the fuel injection period of one stroke), intake air for detecting the intake gas temperature of the intake system A temperature sensor 17, an exhaust temperature sensor 18 for detecting the exhaust gas temperature of the exhaust system, a coolant temperature sensor 19 for detecting the coolant temperature of the engine 70, a fuel temperature sensor 20 for detecting the fuel temperature in the common rail 120, and a DPF Differential pressure sensor 68 (upstream exhaust pressure sensor 68a and downstream exhaust pressure sensor 68b) There has been connected.

  An electromagnetic solenoid of each fuel injection valve 119 for the four cylinders of the engine is connected to the output side of the ECU 11. That is, the high-pressure fuel stored in the common rail 120 is injected from the fuel injection valve 119 in a plurality of times during one stroke while controlling the fuel injection pressure, the injection timing, the injection period, and the like, so that nitrogen oxide (NOx ), And complete combustion with reduced generation of soot and carbon dioxide is performed to improve fuel efficiency. Further, on the output side of the ECU 11, an intake throttle device 81 for adjusting the intake pressure (intake amount) of the engine 70, an exhaust throttle device 82 for adjusting the exhaust pressure of the engine 70, and a failure notification of the ECU 11 are notified. An ECU failure lamp 22, an exhaust temperature warning lamp 23 for notifying an abnormally high exhaust gas temperature in the DPF 50, a regeneration lamp 24 that is turned on when the DPF 50 is regenerated, and the like are connected.

  As shown in FIG. 8, the work machine controller 271 includes various output-related electromagnetic valves, that is, a forward clutch electromagnetic valve 253 for the forward hydraulic clutch 252, a reverse clutch electromagnetic valve 255 for the reverse hydraulic clutch 254, and a sub-shift. A high-speed clutch electromagnetic valve 251 for the hydraulic cylinder 250, a proportional control valve 213 for operating the main transmission hydraulic cylinder 243 in proportion to the operation amount of the main transmission lever 201, a four-drive hydraulic electromagnetic valve 257 for the four-drive hydraulic clutch 256, and double speed Hydraulic oil is supplied to the double speed hydraulic solenoid valve 259 for the hydraulic clutch 258, the left and right autobrake solenoid valves 246, the PTO clutch hydraulic solenoid valve 249 for the PTO clutch 248, and the lift control hydraulic cylinder 215 of the work machine lift mechanism 160. A control electromagnetic valve 211 and the like are connected.

  Further, the work machine controller 271 includes various sensors and switches related to input, that is, a steering potentiometer 290 that detects the amount of rotation (steering angle) of the steering handle 149, and the forward and backward switch lever 198 from the operation position. A forward / reverse potentiometer 291 that detects the on / off state of the reverse hydraulic clutches 252, 254, a main transmission output shaft rotation sensor 292 that detects the output rotation speed of the main transmission output shaft 237, and a throttle position sensor that detects the operating position of the throttle lever 197 16, a vehicle speed sensor 25 for detecting the rotational speed (vehicle speed) of the front and rear four wheels 143, 144, a four-wheel drive mode switch 293 for switching the four-wheel drive hydraulic solenoid valve 257, and a double speed mode switch 294 for switching the double-speed hydraulic solenoid valve 259 , Brake pedal that detects the presence or absence of depression of the brake pedal 191 Switch 295, an auto brake switch 296 for switching the auto brake solenoid valve 246, a main shift potentiometer 297 for detecting the operation position of the main shift lever 201, a sub shift lever sensor 298 for detecting the operation position of the sub shift lever 195, and A minimum rotation speed dial 27 and the like for setting the minimum rotation speed Na of the engine 70 are electrically connected.

  Here, the minimum rotation speed dial 27 changes and adjusts the position of the knob in a continuous (analog) or stepwise (digital) manner so that the minimum rotation speed Na is lower than the low idle rotation speed Nlow inherent to the engine 70. It is configured so that it can be arbitrarily adjusted within a large range. The rotation speed N when the throttle lever 197 is operated to the lowest speed side is the lowest rotation speed Na set by the lowest rotation speed dial 27.

  As can be understood from the above description, in the work vehicle 141 including the engine 70 mounted on the traveling machine body 142 and the common rail fuel injection device 117 that injects fuel into the engine 70, the minimum rotation of the engine 70 is achieved. Since the speed Na can be changed within a range in which the speed Na is larger than the low idle rotational speed Nlow inherent to the engine 70, a higher output horsepower can be easily ensured than the engine 70 having the same displacement. In other words, the engine can have a lower displacement than the engine 70 having the same output horsepower. Therefore, there is an effect that the downsizing of the engine 70 can be easily realized. In addition, since a supercharger is not required to secure output horsepower, there is an effect that the cost of parts can be suppressed.

  In the EEPROM 33 of the ECU 11 or the EEPROM 283 of the work machine controller 271, an output characteristic map M (see FIG. 10) indicating the relationship between the rotational speed N of the engine 70 and the torque T is stored in advance. The output characteristic map M is obtained by experiments or the like. In the output characteristic map M shown in FIG. 10, the rotational speed N is taken on the horizontal axis and the torque T is taken on the vertical axis. The output characteristic map M is a region surrounded by a solid line Tmx drawn upwardly. A solid line Tmx is a maximum torque line representing the maximum torque for each rotational speed N.

  The ECU 11 basically obtains the torque T of the engine 70 from the rotational speed detected by the engine speed sensor 14 and the injection pressure / injection period of each injector 115 and uses the torque T and the output characteristic map M to target fuel. Fuel injection control for calculating the injection amount and operating the common rail device 117 based on the calculation result is executed. The fuel injection amount of the common rail device 117 is adjusted by adjusting the valve opening period of each fuel injection valve 119 and changing the injection period of each injector 115.

(6). First Example of Fuel Injection Control Next, a first example of fuel injection control by the ECU 11 will be described with reference to FIGS. 10 and 11. In the first embodiment, the rotational speed N of the engine 70 is limited to only two types N # 1 and N # 2, and the rotational speed N can be changed to any of the two types N # 1 and N # 2. The ECU 11 is configured to execute rotational speed limitation control for changing and adjusting the speed ratio of the continuously variable transmission 159 so that the vehicle speed V of the traveling machine body 142 is not changed before and after the change.

  The rotational speed limitation control is executed as shown in the flowchart of FIG. That is, the detection value of the engine speed sensor 14 is read to determine whether or not the current rotational speed N is the low speed side N # 1 (S201). If it is not the low speed side N # 1 (S201: NO), the fuel injection amount of the common rail device 117 is adjusted so that the rotational speed N of the engine 70 becomes the low speed side N # 1 (S202), and then the process returns to step S201.

  If it is the low speed side N # 1 in step S201 (S201: YES), the detection value (current torque Tx) of the throttle position sensor 16 is read, and from the rotational speed N # 1, torque Tx and output characteristic map M, A current engine load factor LFx is calculated (S203), and it is determined whether or not the current engine load factor LFx exceeds a predetermined value X (S204). Here, the engine load factor means a ratio to the maximum torque T (maximum engine load) at an arbitrary rotational speed N.

  If the current engine load factor LFx is equal to or less than the predetermined value X (S204: NO), the process returns to step S201. If it exceeds the predetermined value X (S204: YES), the fuel injection amount of the common rail device 117 is adjusted so that the rotational speed N of the engine 70 becomes the high speed side N # 2 (S205). Next, the detected value Vx (vehicle speed) of the vehicle speed sensor 25 is read, and it is determined whether or not the vehicle speed Vx remains before the rotational speed is changed (S206). If the vehicle speed Vx has changed (S206: NO), the gear ratio of the continuously variable transmission 159 in the transmission case 157 is changed and adjusted in order to return the vehicle speed of the traveling machine body 142 to before the rotational speed change (S207), and the process goes to step S206. Return.

  If the vehicle speed Vx is maintained as it was before the rotational speed change in step S206 (S206: YES), then the detected value of the engine speed sensor 14 is read and whether or not the current rotational speed N is the high speed side N # 2. Is determined (S208). If it is not the high speed side N # 2 (S208: NO), the fuel injection amount of the common rail device 117 is adjusted so that the rotational speed N of the engine 70 becomes the high speed side N # 2 (S209), and then the process returns to step S208.

  If it is the high speed side N # 2 in step S208 (S208: YES), the detected value (current torque Ty) of the throttle position sensor 16 is read, and from the rotational speed N # 2, torque Ty and output characteristic map M, A current engine load factor LFy is calculated (S210), and it is determined whether or not the current engine load factor LFy is less than a predetermined value Y (S211). If the current engine load factor LFy is equal to or greater than the predetermined value Y (S211: NO), the process returns to step S206. If it is less than the predetermined value Y (S211: YES), the fuel injection amount of the common rail device 117 is adjusted so that the rotational speed N of the engine 70 becomes the low speed side N # 1 (S212), and the process returns to step S201.

  According to the above control, in the work vehicle 141 including the engine 70 mounted on the traveling machine body 142 and the common rail fuel injection device 117 for injecting fuel to the engine 70, the rotational speed N of the engine 70 is Since the engine is limited to only two types, N # 1 and N # 2, the engine 70 does not use a low rotation range with a small output torque, and the output horsepower is higher than that of the engine 70 with the same displacement. Can be secured. In other words, the engine 70 has a lower displacement than that of the engine 70 having the same output horsepower. Therefore, there is an effect that the downsizing of the engine 70 can be easily realized.

  In particular, when the rotational speed N of the engine 70 is changed to any one of the two types N # 1 and N # 2, the continuously variable transmission 159 does not change the vehicle speed of the traveling machine body 142 before and after the change. Since the gear ratio is changed and adjusted, for example, even if the rotational speed N is set to the low speed side N # 1 or the high speed side N # 2, the vehicle speed of the traveling machine body can be maintained as it was before the rotational speed change. For this reason, there is an effect that the uncomfortable feeling due to the change in the rotation speed of the engine 70 can be eliminated.

(7). Second Example of Fuel Injection Control Next, a second example of fuel injection control by the ECU 11 will be described with reference to FIGS. In a state in which the traveling machine body 142 is stopped, the ECU 11 in principle has the common rail so that the rotational speed N detected by the engine speed sensor 14 matches the minimum rotational speed Na preset by the minimum rotational speed dial 27. The fuel injection amount of the device 117 is feedback-controlled. In other than the stop state, the ECU 11 feedback-controls the fuel injection amount of the common rail device 117 so that the rotational speed N of the engine 70 matches the rotational speed corresponding to the operation position of the throttle lever 197.

  A series of equal fuel consumption rate curves FL is represented in the output characteristic map M of FIG. The equal fuel consumption rate curve FL is a curve like a contour line connecting points of equal fuel consumption rates, and represents a so-called good fuel consumption state with less fuel consumption on the inner peripheral side. According to the equal fuel consumption rate curve FL in this case, the best fuel consumption region exists on the high speed and high torque side of the engine 70. In the output characteristic map M of FIG. 12, the equal fuel consumption rate curve FL is indicated by a broken line. The output characteristic map M also shows an optimum fuel consumption line FS connecting the points where the fuel efficiency of the engine 70 is the best. By changing and adjusting the fuel injection amount so that the engine operating point Q related to the rotational speed N and torque T of the engine 70 is along the optimal fuel consumption line FS, low fuel consumption operation of the engine 70 can be realized. In the output characteristic map M of FIG. 12, the optimum fuel consumption line FS is indicated by a one-dot chain line.

  The output characteristic map M also shows a series of equal output lines PL. The equal output line PL is a line indicating the relationship between the rotational speed N and the torque T when the output horsepower of the engine 70 is constant. Since the product of the rotational speed N and the torque T is proportional to the output horsepower, the output characteristic map M in FIG. In the output characteristic map M of FIG. 12, the equal output line PL is indicated by a two-dot chain line.

  As an example of fuel injection control, the ECU 11 sets the minimum vehicle speed Vlow (creep speed) of the traveling machine body 142 at the low idle rotation speed Nlow when the minimum rotation speed Na larger than the low idle rotation speed Nlow is set. In order not to change, the minimum vehicle speed control for changing and adjusting the transmission ratio of the continuously variable transmission 159 can be executed. Further, when the engine operating point Q deviates from the preset optimum fuel consumption line FS, the ECU 11 shifts the engine operating point Q to the optimum fuel consumption line FS and does not change the vehicle speed V of the traveling machine body 142. As described above, the optimum fuel consumption control for changing and adjusting the gear ratio of the continuously variable transmission 159 is also executable. The algorithm shown in the flowcharts of FIGS. 13 to 16 is stored in the EEPROM 33. By calling the algorithm to the RAM 34 and processing it by the CPU 31, the minimum vehicle speed control and the optimum fuel efficiency control are executed.

  The minimum vehicle speed control is executed, for example, as follows (see FIG. 13). Here, the set value of the minimum rotation speed dial 27 is the minimum rotation speed Na larger than the low idle rotation speed Nlow, and the minimum rotation speed of the engine 70 when the throttle lever 197 is operated to the minimum speed side is the set value Na. Suppose that First, it is determined whether or not the brake pedal 191 is operating (S01). If it is not operating (S01: NO), the detected value of the engine speed sensor 14 and the low idle rotation stored in advance in the ROM 32 or the EEPROM 33 are determined. The minimum vehicle speed Vlow when the speed is Nlow is read (S02). Next, if the throttle position sensor 16 is off (S03: off) and the detected value of the engine speed sensor 14 is the set value Na of the minimum rotation speed dial 27 (S04: YES), then the traveling body 142 The transmission ratio of the continuously variable transmission 159 in the transmission case 157 is changed and adjusted so that the minimum vehicle speed remains unchanged at the minimum vehicle speed Vlow at the low idle rotation speed Nlow (S05, transmission ratio control).

  The speed ratio control during the minimum vehicle speed control (speed ratio control in step S05) is executed, for example, as shown in the flowchart of FIG. That is, the current detection value V1 (vehicle speed) of the vehicle speed sensor 25 is read (S101), and if the current vehicle speed V1 is greater than the lowest vehicle speed Vlow read in step S02 (S102: YES), the continuously variable transmission 159. Is reduced (S103), and the process returns to step S102. If the current vehicle speed V1 is smaller than the minimum vehicle speed Vlow (S104: YES), the transmission ratio of the continuously variable transmission 159 is increased (S105), and the process returns to step S102. If the minimum vehicle speed Vlow and the current vehicle speed V1 are the same (S104: NO), the state is maintained and the process returns.

  As can be seen from the above description, the continuously variable transmission 159 for shifting the power from the engine 70 is provided, and when the minimum rotational speed Na is set to a value larger than the low idle rotational speed Nlow, Since the speed ratio of the continuously variable transmission 159 is changed and adjusted so that the minimum vehicle speed of the traveling body 142 remains unchanged at the low idle rotational speed Nlow (Vlow), the minimum rotational speed Na is set to the low idle speed. Even if the rotational speed is made higher than the low speed Nlow, the minimum vehicle speed (creep speed) of the traveling machine body 142 is not increased, and can be maintained at the low idle rotational speed Nlow (Vlow). For this reason, when traveling at low speed, there is an effect that traveling performance (vehicle speed without a sense of incongruity) that is the same as that of the work vehicle 141 equipped with the engine 70 having the same displacement is obtained.

  For example, the optimum fuel consumption control shown in FIG. 15 is executed as follows. That is, the detected value of the engine speed sensor 14 (current rotational speed N1) and the detected value of the throttle position sensor 16 (current torque T1) are read (S11), and the current engine operating point is output using the output characteristic map M. Q1 is obtained (S12), and it is determined whether or not the current engine operating point Q1 is on the optimum fuel consumption line FS (S13). If the current engine operating point Q1 deviates from the optimum fuel consumption line FS (S13: NO), from the relationship between the current engine operating point Q1 and the optimum fuel consumption line FS and the equal output line PL of the output characteristic map M, It is determined whether or not there is a target engine operating point Q2 having the same output horsepower as the current engine operating point Q1 and on the optimum fuel consumption line FS (S14). Since the current engine operating point Q1 and the target engine operating point Q2 have the same output horsepower, they are located on a common iso-output line PL.

  If there is a target engine operating point Q2 (S14: YES), the current value detected by the vehicle speed sensor 25 (vehicle speed V1) and the rotational speed R1 of the main transmission output shaft 237 are read (S15), and then the common rail device 117 The fuel injection amount is adjusted to shift the engine operating point from the current Q1 to the target engine operating point Q2 (S16). Then, by correcting the applied voltage of the proportional control valve 213 according to a command from the work machine controller 271, the main transmission hydraulic cylinder 243 is operated to change and adjust the inclination angle of the pump swash plate 242 in the hydraulic pump unit 240, The amount of hydraulic oil supplied to the hydraulic motor unit 241 is controlled, and the gear ratio of the continuously variable transmission 159 is changed and adjusted so that the rotational speed R of the main transmission output shaft 237 is maintained at the detection value R1 in step S06. (Gear ratio control, S17). Here, the gear ratio refers to the ratio (R / N) of the rotational speed R of the main transmission output shaft 237 to the rotational speed N of the engine 70.

  The speed ratio control during the optimal fuel consumption control (speed ratio control in step S17) is basically the same mode as the speed ratio control during the minimum vehicle speed control, and is executed as shown in the flowchart of FIG. 16, for example. That is, the vehicle speed V2 after the transition to the engine operating point Q2 is read (S111), and if the post-transition vehicle speed V2 is larger than the pre-transition vehicle speed V1 read in step S15 (S112: YES), the main transmission output shaft 237 The gear ratio of the continuously variable transmission 159 is decreased so that the rotation speed R becomes the detected value R1 in step S06 (S113), and the process returns to step S112. If the post-transition vehicle speed V2 is smaller than the pre-transition vehicle speed V1 (S114: YES), the gear ratio of the continuously variable transmission 159 is set so that the rotational speed R of the main transmission output shaft 237 becomes the detection value R1 in step S15. (S115), and the process returns to step S112. If the vehicle speed V1 before the transition and the vehicle speed V2 after the transition are the same (S114: NO), the state is maintained and the process returns.

  As can be seen from the above description, when the engine operating point Q related to the rotational speed N and torque T of the engine 70 deviates from the preset optimum fuel consumption line FS, the engine operating point Q is set to the optimum fuel consumption line. Since the speed ratio of the continuously variable transmission 159 is changed and adjusted so that the vehicle speed V of the traveling machine body 142 is not changed and the vehicle speed V of the traveling machine body 142 is not changed, the rotational speed N It is possible to reliably prevent the fluctuation of the vehicle speed V accompanying the change in the vehicle speed. Therefore, the work vehicle 141 has an effect that stable running performance can be obtained.

  17 and 18 show another example of the fuel injection control. In another example, when the engine 70 is overloaded or close to the engine 70, the engine load factor LF is reduced by shifting to the target engine operating point Q2 ′ on the high speed low torque side where the output horsepower is the same. Is effectively addressed, and the future exhaust gas regulations will be strengthened properly.

  Another example of the fuel injection control is executed as follows (see FIG. 18). Here, the engine 70 is subjected to isochronous control that keeps the rotational speed N constant regardless of load fluctuations. The rotational speed N is fixed to the rotational speed N1 ′ (see FIG. 17) by the throttle lever 197. It shall be. During isochronous control, when the rotational speed N1 ′ of the engine 70 is determined by the throttle lever 197, the high-speed rotational speed N2 ′ is automatically set correspondingly.

  First, the detected value (current rotational speed N1 ′) of the engine speed sensor 14 and the detected value (current torque T1 ′) of the throttle position sensor 16 are read (S21), and these detected values N1 and T1 are output. A current engine load factor LF1 ′ is calculated using the characteristic map M (S22), and it is determined whether or not the current engine load factor LF1 ′ is equal to or greater than a predetermined value X (S23).

  If the current engine load factor LF1 ′ is equal to or greater than the predetermined value X (S23: YES), the current engine operating point Q1 ′, the equal output line PL of the output characteristic map M, and the high speed side rotational speed N2 ′ From the relationship, a target engine operating point Q2 'on the high speed and low torque side having the same output horsepower as the current engine operating point Q1' and having an engine load factor LF smaller than a predetermined value X is obtained (S24). Thereafter, the detected value (vehicle speed V1 ′) of the vehicle speed sensor 25 and the rotational speed R1 ′ of the main transmission output shaft 237 are read (S25), the fuel injection amount of the common rail device 117 is adjusted, and the engine operating point is set. The current engine speed Q1 'is shifted to the target engine operating point Q2' to increase the rotational speed (N1 '→ N2', S26). Then, by correcting the applied voltage of the proportional control valve 213 according to a command from the work machine controller 271, the main transmission hydraulic cylinder 243 is operated to change and adjust the inclination angle of the pump swash plate 242 in the hydraulic pump unit 240, The amount of hydraulic oil supplied to the hydraulic motor unit 241 is controlled, and the gear ratio of the continuously variable transmission 159 is changed and adjusted so that the rotational speed R of the main transmission output shaft 237 remains at the detection value R1 in step S25. (Gear ratio control, S27).

  Next, after calculating the changed engine load factor LF2 ′ from the changed rotation speed N2 ′ and torque T2 ′ (S28), it is determined whether or not the engine load factor LF2 ′ is equal to or smaller than a predetermined value Y (S28). S29). If the engine load factor LF2 ′ after the change is equal to or less than the predetermined value Y (S29: YES), the fuel injection amount of the common rail device 117 is adjusted to change the engine operating point from the target engine operating point Q2 ′ to the original engine operating point. The process proceeds to Q1 '(S30). Then, by correcting the applied voltage of the proportional control valve 213 according to a command from the work machine controller 271, the main transmission hydraulic cylinder 243 is operated to change and adjust the inclination angle of the pump swash plate 242 in the hydraulic pump unit 240, The amount of hydraulic oil supplied to the hydraulic motor unit 241 is controlled, and the gear ratio of the continuously variable transmission 159 is changed and adjusted so that the rotational speed R of the main transmission output shaft 237 remains at the detection value R1 in step S25. (S31). Note that the gear ratio control in steps S27 and S31 is the same as that in the flowchart of FIG. 16, and thus detailed description thereof is omitted.

  If the control is performed as described above, the engine 70 can be driven efficiently without being continuously driven when the engine 70 is overloaded or close to it (the engine 70 can be driven with a margin). For this reason, for example, it becomes possible to take an appropriate measure against future exhaust emission regulations such as the next EPA regulations.

(8). Others The present invention is not limited to the above-described embodiment, and can be embodied in various forms. The configuration of each part is not limited to the illustrated embodiment, and various modifications can be made without departing from the spirit of the present invention.

11 ECU (control means)
70 Engine 117 Common rail device (fuel injection device)
120 common rail 141 tractor (work vehicle)
142 traveling machine body 159 continuously variable transmission

Claims (3)

In a work vehicle including an engine mounted on a traveling machine body and a common rail fuel injection device that injects fuel into the engine,
The minimum rotation speed of the engine can be changed in a range that is larger than the low idle rotation speed unique to the engine.
Drive system control device for work vehicle. A continuously variable transmission for shifting power from the engine;
When the minimum rotational speed is set to a value larger than the low idle rotational speed, the speed ratio of the continuously variable transmission is set so that the minimum vehicle speed of the traveling body remains unchanged at the low idle rotational speed. Change the adjustment,
A drive system control device for a work vehicle according to claim 1. When the engine operating point related to the rotational speed and torque of the engine is out of the preset optimum fuel consumption line, the engine operating point is shifted to the optimum fuel consumption line, and the vehicle speed of the traveling machine body is not changed. Changing and adjusting the gear ratio of the continuously variable transmission;
A drive system controller for a work vehicle according to claim 2.

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